Using Marijuana before the Age of 15 Increases Risk of Psychotic Disorders

Teens that start smoking marijuana before the age of 15 are twice as likely to develop a psychotic disorder by the age of 21 as teens that don’t smoke marijuana.

An Australian research study done on siblings has found that
teens that start using marijuana at 15 or younger have a significantly higher
risk of psychotic disorders.

Australian scientists enlisted 3801 young adults born in Brisbane Australia
between 1981 and 1984 (many were sibling pairs) to participate in the study.
Study subjects were asked at the age of 21 about their history of marijuana use
and whether they’d ever had any incidences of hallucinations or delusions, or
had experienced any psychotic disorders, such as schizophrenia.

Sibling pairs were used when possible to minimize genetic
and environmental differences that can otherwise confound results.

The researchers found that:

Those
that used marijuana for 6 years or longer (initiated use prior to the age
of 15) were twice as likely to develop schizophrenia or another delusional
disorder as those that had never used marijuana

Subjects
who had used marijuana for the longest period of time were more likely to
score highly on tests for psychotic experiences

Lead researcher John McGrath says that the results of this
study confirm other studies which have also found an association between marijuana
use and an increased likelihood of a psychotic disorder, saying “The evidence
is really mounting up.”

He says that although his study didn’t factor in the amount
teens were smoking that earlier studies have shown a link between quantity of
use and risk of psychosis. Where his study adds to the knowledge base, says McGrath,
is by showing that an earlier age of initiation causes an increased rate of
psychosis. He explains, saying, “What we think it suggests is that the
adolescent brain is more vulnerable to drug abuse.”

McGrath says that young people need to know that marijuana
may not be as harmless as they perceive it to be. He cautions, "Everything
we do has risks involved - whether we drive or ride a bike or use alcohol - and
I think it's important that young people know that if you use cannabis from an
early age you do increase your risk of a psychotic disorder."

Helpful Reading:

Thinking about giving up marijuana but not sure you’re ready to take the plunge? Well, here are 70 benefits of quitting – all first-hand accounts from previously heavy users about how life changes for the better once you don’t need to get high all the time.